Known gas turbines can include combustors wherein compressed air coming from the compressor is fed and mixed with a gaseous or liquid fuel that is combusted in the combustor.
Under certain conditions, such as when low emissions are pursued or at part load, for example, pressure oscillations can be generated in the combustor due to thermo acoustic instabilities. These pressure oscillations can cause structural damages or excessive wear of the gas turbine components and, in addition, a noisy operation.
In an effort to guarantee an acceptable gas turbine lifetime and control noise, pressure oscillations during operation of the gas turbine should be damped.
In known implementations damping can be achieved by passive damping structures. Examples of these passive damping structures are Helmholtz resonators, quarter-wave tubes, screen or perforated screech liners. During manufacture, known gas turbines are first designed and optimized without passive damping structures. Passive damping structures can be later added, as necessary, based on desired results of a specified implementation. As a result, in order to provide proper cooling of damping structures, cooling air should be diverted from other gas turbine regions, causing an increase in operating temperature and shortening its operational lifetime.
In addition, as often as air is taken away from the combustor (or in sequential combustion gas turbines from the first combustor) the flame temperature increases thus increasing the NOx emissions.
U.S. Pat. No. 7,104,065 discloses a damping arrangement for a combustor with a two-walled combustion chamber and a further outer wall defining a gastight volume connected to the inner of the combustion chamber. In addition to the drawbacks already described, this damping arrangement is functionally separated from the other components of the combustor and, moreover, it proved difficult to incorporate it in the combustor, due to the limited space available.